The present invention relates to disposable absorbent articles such as disposable diapers, sanitary napkins, and the like.
Disposable diapers provide substantial advantages and convenience over diapers that have to be laundered and reused, particularly when the diapers are used away from home. In recent years, many different disposable diapers have been proposed and some have been successful in the marketplace. However, even the successful diapers may be inadequate in functioning properties, and their commercial success has come at least in part, because consumers have been willing to accept inadequate performance as part of the price for convenience.
One design criterion which has not heretofore been met adequately is keeping moisture away from the surface of the diaper which comes into contact with the infant's skin to thereby avoid skin irritation and infection, while at the same time handling a full volume discharge of urine.
One disposable diaper representing a significant advance in the art is a multilayer diaper comprising, in order, a fibrous facing layer which is to be brought into contact with the infant's skin, a layer of a highly porous, loosely compacted cellulosic batt, a paper-like densified, highly compacted cellulosic fibrous layer integral with the loosely compacted batt, and an impervious backing sheet adhered to the densified layer at the interface therebetween. The facing layer is of porous construction and its fibers have less wettability for water than the fibers of the loosely compacted batt, resulting in a tendency for liquid to flow from the facing layer into the batt. The densified fibrous layer has a smaller average pore size than the loosely compacted batt, resulting in a tendency for liquid to flow preferentially from the batt into the underlying densified layer rather than to other areas of the batt, thus tending to restrict wetting in the batt to an area of moderate size. Liquid flowing into the densified layer tends to spread laterally because of the wicking action of the densified layer and liquid which might pass through the densified layer during discharge is held back by the impervious backing sheet usually for a sufficient time to permit absorption to take place. Liquid in excess of the absorptive capacity of the densified layer is forced back by the impervious layer into the dry portion of the loosely compacted batt, thus utilizing the additional absorptive capacity therein.
However, while the diaper structure described above represents a significant advance in the art, particularly in its ability to maintain the layer in contact with an infant's skin dry, during periods of heavy discharge, after the densified layer and integral loosely compacted batt become saturated over a sufficient area, there is a tendency for urine to wet back into the facing layer.